Most conventional communication is enabled via optical fiber or twisted-pair cable. Specifically, communication via optical fiber is characterized by a long transmission distance, low distortion, anti-disturbance, etc., while communication via twisted-pair cable is characterized by simple accessing, good compatibility with other apparatus, etc. Optical fiber transceivers are provided with characteristics of both of the above-mentioned modes of communication, so that the two modes can be converted to each other. The optical transceiver is a key subassembly for optical fiber transceivers and is configured to enable inter-conversion between light and electricity. Therefore, the performance of an optical transceiver has a direct impact on the whole transceiver and determines parameters of the transceiver such as communication distance, signal rate, error rate, etc. In a conventional bi-directional fiber optic transceiver, a wave separator or splitter is mounted at a 45-degree angle between a laser diode and the fiber, and the laser diode converts electronic signals into optical signals, which are provided to the fiber via the wave separator or splitter. Input optical signals from the fiber are reflected by the wave separator or splitter, and then are received along the input optical path by a photodiode configured to convert optical signals into electronic signals. The light from the laser diode has an emission angle which is larger than the acceptance angle of a fiber with low aperture value. As a result, if such laser diode and fiber are directly coupled, it causes serious energy loss. Therefore, how to couple the emission power of the optical source to the fiber in an optical transmitter for transmission is significant.
As FIG. 1 shows, in order to solve this problem and increase coupling efficiency, a lens 400 is mounted between laser diode 300 and fiber 600. Laser diode 300 modulates an electronic signal into one that has no inclined ray when it goes through lens 400. This process is characterized by a low imaging difference, high coupling rate, short focal length and low cost. Additionally, divergent beams from a light-emitting diode can be changed into convergent beams or collimated beams using lens 400. The optical source and fiber in a bi-directional fiber optic transceiver can have high coupling efficiency, with emitted light from laser diode 300 converging on lens 400. Generally, lens 400 is mounted between laser diode 300 and wave separator or splitter 500 in the direction of laser diode 300 in the optical transceiver so as to increase the coupling ratio of laser diode 300 and fiber 600. In addition, a hemispherical lens at a surface of photodiode 100 plays a role in short focus to increase the coupling ratio between photodiode 100 and fiber 600. However, in this way, the optical transceiver has a larger size, so that the structural dimensions of the bi-directional optical fiber subassembly in a slightly larger size is incompatible with an SFP+ profile in a smaller housing.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.